Conformational energies have been determined by Fourier transform infrared (FT IR) spectroscopy for isotactic, atactic, and syndiotactic PMMA's and the results have been compared with rotational isomeric state (RIS) calculations. Results for syndiotactic PMMA by FT IR (2000 cal/mol) are in good agreement with RIS calculations (1900 cal/mol), but FT IR results for isotactic PMMA indicate a lower conformational energy (700 cal/mol). Conformational energies for the side chain vary from 700 to 900 cal/mol with tacticity.Conformational contributions to the specific heat change at the glass temperature are calculated and compared with experimental results and previous analyses. The constancy of AH/RTg predicted by the Gibbs-DiMarzio theory is found not to hold. AH/RTg varies from 1.2 to 2.6 with tacticity. Other factors, such as the conformation and packing of side chains, must influence the glass transition process.

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The recovery of polyvinyl chloride glasses prepared at high temperature and pressure (120 °C, 7 kbar) have been observed using Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). Changes in absorbance associated with conformational reequilibration occur above 80 °C, the normal glass temperature of polyvinyl chloride (PVC). Peaks are observed in Cp 15–20 °C below Tg which are attributed to relaxation of volume strain or holes. Since the enthalpy and the conformational recovery occur at different temperatures and time scales, we conclude that neither free volume models nor flexed bond models are adequate to explain the properties of glasses prepared at high pressure.

The pressure‐induced freezing of high‐energy conformations (trans‐gauche) of poly(vinyl chloride) has been measured by FTIR absorbance spectroscopy. The conformational change predicted from the increase in Tg with pressure and the change in population (absorbance) with temperature is larger than the observed change in population (absorbance). This difference is of the right order of magnitude as that predicted from the volume difference between conformers which favors the trans isomer at high pressure. Samples prepared at high pressure recover to their equilibrium population at the normal zero‐pressure glass temperature when heated with no applied pressure.

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The conformational and enthalpic changes that occur in poly(vinyl chloride) (PVC) glasses that have been vitrified from the melt under pressure have been examined by Fourier transform infrared spectroscopy and quantitative differential scanning calorimetry. It is shown that these pressures freeze in the high energy states that are characteristic of the vitrification temperature and increase the apparent glass transition temperature of the polymer. In addition, pressures in excess of the vitrification pressure, cause intermolecular effects that can be relaxed out below Tg. Both of these processes create characteristic endothermic and exothermic changes in the apparent heat capacity of the glass that appear over a period of time and are sensitive functions of the glass formation processes as well as the subsequent annealing history. The endothermic events are interpreted as the stress perturbed volumetric relaxation process white the exotherms are associated withh the release of the frozen in stresses.